The new IWC tube (Inside Diameter & Weight Controlled) was developed for the steam piping market with a large diameter in high allied steel (9% chrome) to be used in thermal power stations. It originated directly from client needs and its manufacture was optimized to be lighter and more accurate than an ASTM pipe, while remaining more competitive than a fully machined pipe.
The narrow tolerance for the inside diameter is a major advantage for the client, as it can ease implementation by welding and optimize steam flow. The dimensional definition, combined with this narrow tolerance, offers a substantial weight decrease of up to 15% when compared with a standard tube. This leads to cost savings for the general structure. Manufacture optimization visibly reduces costs, compared to fully machined pipes.
In general, internal pull boring and external grinding help obtain the necessary dimensional accuracy. For tube sizes outside of the standard range, Vallourec has developed its own machining technique: rapid turning.
The Düsseldorf-Reisholz plant has adapted to increased demand in IWC pipes by investing in machining technologies. To ensure that tolerances remain in the specified range, the pipe is placed on steady rests which allow for fast machining speeds and very narrow tolerances for the finished product.
Drawing on its worldwide experience in tubular solutions, Vallourec has provided IWC pipes for many advanced thermal power stations in China and Korea over the last few years.